Abstract
One-step adsorptive purification of ethylene (C2H4) from four-component gas mixtures comprising acetylene (C2H2), ethylene (C2H4), ethane (C2H6) and carbon dioxide (CO2) is an unmet challenge in the area of commodity purification. Herein, we report that the ultramicroporous sorbent Zn-atz-oba (H2oba = 4,4-dicarboxyl diphenyl ether; Hatz = 3-amino-1,2,4-triazole) enables selective adsorption of C2H2, C2H6 and CO2 over C2H4 thanks to the binding sites that lie in its undulating pores. Molecular simulations provide insight into the binding sites in Zn-atz-oba that are responsible for coadsorption of C2H2, C2H6 and CO2 over C2H4. Dynamic breakthrough experiments demonstrate that the selective binding exhibited by Zn-atz-oba can produce polymer-grade purity (>99.95%) C2H4 from binary (1:1 for C2H4/C2H6), ternary (1:1:1 for C2H2/C2H4/C2H6) and quaternary (1:1:1:1 for C2H2/C2H4/C2H6/CO2) gas mixtures in a single step.
Highlights
One-step adsorptive purification of ethylene (C2H4) from four-component gas mixtures comprising acetylene (C2H2), ethylene (C2H4), ethane (C2H6) and carbon dioxide (CO2) is an unmet challenge in the area of commodity purification
The presence of impurities is a consequence of the steam pyrolysis process used to produce C2H4, which in turn results in acetylene (C2H2), carbon dioxide (CO2), ethane (C2H6) and other downstream products including propylene (C3H6), propane (C3H8), hydrogen (H2), C4 and higher light hydrocarbons[3,4], which are separated by the difference of boiling points
Since polarization contributes to less than 10% of the total energy for simulations of all four gases in Zn-atz-oba, the overestimation of the theoretical uptakes compared with experiment might be attributable to the partial charges (Supplementary Data 1) and/or the repulsion/dispersion parameters (Supplementary Data 2) that were used for the metalorganic frameworks (MOFs) atoms
Summary
One-step adsorptive purification of ethylene (C2H4) from four-component gas mixtures comprising acetylene (C2H2), ethylene (C2H4), ethane (C2H6) and carbon dioxide (CO2) is an unmet challenge in the area of commodity purification. We report that the ultramicroporous sorbent Zn-atz-oba (H2oba = 4,4-dicarboxyl diphenyl ether; Hatz = 3-amino1,2,4-triazole) enables selective adsorption of C2H2, C2H6 and CO2 over C2H4 thanks to the binding sites that lie in its undulating pores. Dynamic breakthrough experiments demonstrate that the selective binding exhibited by Zn-atz-oba can produce polymer-grade purity (>99.95%) C2H4 from binary (1:1 for C2H4/ C2H6), ternary (1:1:1 for C2H2/C2H4/C2H6) and quaternary (1:1:1:1 for C2H2/C2H4/C2H6/ CO2) gas mixtures in a single step. The interplay of packing sequence and gas mass transfer in SSST can make industrial-scale processes infeasible and, as illustrated, a single sorbent that coadsorbs C2H2, C2H6, and CO2 would be desirable for quaternary gas separations such as the purification of C2H4 from a C2H2-C2H4-C2H6-CO2 mixture. We report that the challenge of one-step C2H4 purification from a quaternary mixture (C2H2-C2H4-C2H6-CO2) is achieved by a single physisorbent, the ultramicroporous coordination network Zn-atz-oba. As calculated by PLATON48, the void space of Zn-atz-oba is 35.9%
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